Fuel Evaporation System Subaru Justy I

DESCRIPTION

The fuel evaporation system prevents fuel vapor from reaching the atmosphere. Major components of the system include a sealed fuel tank with integral expansion chamber, vacuum relief filler cap, vapor separator, 2-way valve, charcoal canister, purge control valve, bowl vent solenoid valve (carbureted engine), purge control solenoid valve (all except carbureted engine), thermo vacuum valve (carbureted engine), control unit (all except carbureted engine), secondary purge line (Turbo), rollover valve (Justy), and connecting lines and hoses.

Scheme 1

CARBURETED ENGINE

When engine is not running, vapor from expanding fuel in fuel tank collects in expansion tank. Vapor flows from expansion tank and into charcoal canister through vapor separator and 2-way valve. The closed purge control valve prevents vapor from flowing out of canister and into intake manifold through purge line. When ignition is off, bowl vent solenoid valve opens to allow float bowl vapor to flow to canister.

When ignition switch is in "ON" or "START" position, bowl vent solenoid valve closes, blocking off float bowl to canister passage. On all models except Justy, the thermo vacuum valve vents control vacuum to air cleaner until coolant temperature exceeds 95°F (35°C). With engine running and coolant temperature greater than 95°F (35°C), thermo vacuum valve opens purge control valve.

On Justy models, Emission Control Module (ECM) controls entry of vapor into intake tract. On all models, manifold vacuum then pulls vapor from canister into combustion chamber for burning.

Scheme 2

Non-Turbo

When engine is not running, vapor from expanding fuel in fuel tank collects in expansion tank. Vapor flows from expansion tank and into charcoal canister through vapor separator and 2-way valve. Intake manifold vacuum controls the purge control valve on the canister. When the purge control valve is opened, vapor flows from the canister into the throttle body.

Scheme 3

Turbo

Fuel travels from fuel tank to canister in the same manner as fuel injected models without turbo with 2 differences. When turbo is in effect, purge control valve is closed by a return spring. Also, an additional purge line purges vapor into the air intake boots when the engine is running.

Scheme 4

MAINTENANCE

Check system for damage or clogged lines, defective valves and defective canister every 30 months or 48,000 miles. Replace canister every 5 years or 96,000 miles. Repair or replace components as necessary.

CHARCOAL CANISTER

1. Remove vacuum hose from canister vacuum vent port. (Scheme 5) Blow air into canister port. Check that air flow is blocked. If air can be blown into canister, diaphragm in purge control valve is ruptured.
2. Disconnect purge vent hose from canister. Blow air into purge vent port. Air flow will be blocked if valve is operating properly.
3. Remove hoses from canister's fuel tank and carburetor ports. Blow air into each port. Check that air flows into canister.
4. On Turbo models, remove secondary purge hose. Blow into hose. Air should flow with little resistance.

Scheme 5

2-WAY VALVE

Remove valve from hoses. Mark hoses for reinstallation. Blow air into each valve port. Check that air flows through valve with light resistance. Visually inspect valve for cracks.

1. Using an ohmmeter, check resistance between positive and negative terminals of solenoid. If resistance is not 32.7-39.9 ohms (16.2-19.8 ohms for Justy), replace solenoid valve.
2. Using an ohmmeter, ensure windings are not grounded. If grounded, replace solenoid valve.
3. Apply battery voltage to valve terminals. Apply vacuum to vacuum passage. Ensure passage opens and closes as voltage is applied and removed. If not, replace solenoid valve.

Remove hoses from valve. Remove valve from vehicle. Blow air into each port. Ensure air flow is blocked. Using a vacuum pump, apply 7.9 in. Hg to solenoid valve port. Blow air into carburetor port. Air should not flow through valve. If it does, replace vacuum valve.

Scheme 6

1. To test thermo vacuum valve, remove valve from engine and connect hoses to valve ports. Cool valve with water, being careful not to submerge valve or allow water to enter valve ports or filter.
2. With valve temperature less than 126°F (52°C), blow air into bowl vent port. Check that air flows out of top filter port and is blocked at lower port to intake manifold.
3. Warm valve with hot water until valve temperature is greater than 153°F (67°C). Seal port to bowl vent and blow air into manifold vacuum port. Check that air flow is blocked with port sealed and that air flows freely out of port when opened.

SYSTEM TESTING

Remove filler cap. Disconnect vent hose between charcoal canister and fuel tank. Blow air toward canister. Check that air flows freely into canister. Blow air toward fuel tank. Check that air flows into tank with a slight resistance from 2-way valve.